A challenge of biomedical research is to compress the period of frailty and disability as people reach advanced age. Cellular senescence, the growth arrest that occurs when cells experience potentially oncogenic insults, has been proposed to contribute to age-related dysfunction. There is as yet no definitive evidence for this. To understand the role of senescent cells in age-related dysfunction, we created a mouse model from which p16-expressing senescent cells can be removed selectively. We devised mechanismbased interventions that interfere with the inflammatory senescence-associated secretory phenotype (SASP), which may be the basis of the inflammation that underlies many age-related diseases and frailty. We discovered a link between the SASP and immune system dysfunction, and found potential ways to break this link. Our unifying hypotliesis is that preventing the accumulation of senescent cells or their effects can restore age-related decrements in function. We propose the following Specific Aims. Aim 1 Eliminate senescent cells. We will use an innovative animal model from which we can selectively remove senescent, potentially cancerous cells to determine if this intervention attenuates development of age-related functional decrements and frailty and enhances healthspan. Aim 2 Inhibit the SASP by manipulating Jak/Stat. We found the SASP is attenuated by inhibiting Jak/Stat, an intervention that dramatically reduces the frailty associated with cancer and hematological disorders. We will test the impact of this intervention onage-related dysfunction. Aim 3 Inhibit the SASP by manipulating mTOR. We also found that inhibiting components of the mTOR pathway inhibits the SASP without interfering with the senescence-associate replicative arrest that defends against cancer. We will determine whether and how this inhibition reduces age-related dysfunction. Aim 4 Break the link between the SASP and inflammasomal activation. We found the SASP activates the inflammasome, while inhibiting it restored immune function in old animals. We will test if inflammasome inhibitors reduce age-related senescent cell accumulation and dysfunction. These Aims will be tested in four Subprojects supported by Administrative, Mouse Phenotyping and Pathological Assessment (MPPA), and Systems Biology/ Bioinformatics Cores. We will use innovative culture systems, novel animal models, and comprehensive healthspan phenotyping to test our hypothesis, focusing on frailty/muscle, metabolic/fat, skin, and immune function initially. Our approach will provide timely, innovative, and clinically relevant interventional results based on addressing the fundamental question of the role of cellular senescence that has remained unanswered for many years.